Method of stabilizing tricot knitted fabrics



United States Patent 3,173,189 METHOD OF STABILIZING TRICOT KNITTED FABRICS Ralph E. Lacy, Charlotte, N.C., assignor to Celanese Corporation of America, New York, N.Y., a corporation of Delaware No Drawing. Filed Apr. 25, 1961, Ser. No. 105,290

3 Claims. (Cl. 28-76) This invention relates to the stabilizing of a knitted fabric of special construction against shrinkage.

Heretofore drapery fabrics have generally been woven so as to take advantage of the inherently relatively low shrinkage and dimensional stability offered in a woven construction. The few attempts to utilize knitted fabrics have been unsatisfactory because of the relatively poor dimensional stability of such fabrics after washing, even when such knitted fabrics have been initially subjected to a stabilizing treatment of one kind or another.

Accordingly, it is an object of this invention to produce a novel shrinkage-resistant knitted fabric.

Another object is to provide a method for stabilizing a specially knitted fabric against shrinkage.

A further object is to provide a specially knitted drapery fabric that is stabilized against shrinkage.

Additional objects and advantages will become apparent from the following detailed description and claims wherein all parts are by weight unless otherwise stated.

In accordance with one aspect of my invention, I have found that a warp knit fabric comprising thermoplastic filamentary material capable of being heat set can be dimensionally stabilized by being first hot wet pretreated to release knitting tensions, and thereafter being heat treated and mechanically compacted. Fabrics so treated are found to retain their dimensions, ie not to shrink or lengthen, even after hot laundering.

The filamentary material making up the fabric advantageously comprises at least about 50% by weight of thermoplastic fibers. While secondary cellulose acetate may be employed, preferably the thermoplastic fiber is crystallizable upon heat treatment, e.g. cellulose triacetate, nylon, polyesters such as polyethylene terephthalate, vinylidene cyanide polymers and copolymers, vinyli dene chloride polymers and copolymers, etc. Blends of these with one another and/ or with non-thermoplastic fibers such as cotton or rayon may also be employed. Either the individual yarns may be so blended, or some warps of a bar may be different from other warps of that bar or the warps of one bar may be the same as one another but different from the warps of another bar.

' As employed herein, fibers includes also continuous filaments.

The knit fabric is pretreated by being wet with water at about 190 F. to the boil for a time upward of 10 seconds. A minute is adequate time although a longer time is permissible. The fabric must be laterally unrestrained so that it is free to contract in lateral dimension Advantageously the lateral contraction may be as much as 10% or even higher, e.g. 13%. This may be assisted by placing the fabric under longitudinal tension.

The fabric, which may be bunched up, may be opened and rinsed in cold water which partially sets the fabric and prevents creasing during further processing such as hot bleaching, dyeing, or the like, which advantageously is effected at this stage.

The fabric is then dried and heat treated without increasing its width and possibly with holding it against further lateral shrinkage such as by use of a tenter frame. The conditions of heat treatment will depend upon the particular identity of the fiber. For example, when operating on cellulose triacetate, hot air at 375 to 400 F. will effect heat treatment in a minute or less, e.g. about 20 3,173,189 Patented Mar. 16, 1965 ice seconds at 385 F. The drying may be effected continuously with the heat treatment, the fabric passing first through a drying section and then into a heat treatment section of a heating unit, the temperature in the drying section being lower than that in the heat treatment section, e.g. about 225 to 250 F.

Finally the fabric is subjected to a mechanical compaction in longitudinal direction to reduce its length to about to 99% and preferably from about 94 to 97% of that before compaction.

Mechanical compaction can be carried out on any equipment available for this purpose such as compressive shrinking apparatus of the type that employs a rubber or felt blanket for holding the fabric against a driven roll such as is shown in United States Patent No. 1,861,- 424. Other suitable apparatuses are described in An Introduction to Textile Finishing by I. T. Marsh, Chapman & Hall Ltd., 1953, pages 248 to 253, and in A Handbook of Textile Finishing by A. J. Hall, Chemical Publishing Co., Inc., 1955, pages 188 to 193.

After longitudinal compaction the fabric may be printed, desirably by roller or screen printing with resin bonded pigments. The printing should be carried out un der conditions that are as tensionless as possible. The degree of wash and crock fastness will, of course, depend upon the nature of the particular printing vehicle used.

While preferably heat treatment precedes longitudinal compaction, the sequence may be changed. If other wet treatment steps such as bleaching or dyeing are to be carried out, they should follow the wet pretreatment and precede the drying.

In accordance with a preferred embodiment of the invention the fabric may be warp knit on two bars. The presence of at least about 20% by weight of crystallizable thermoplastic fibers in the yarns of both bars ensures relatively high strength and dimensional stability for the fabric in both lateral and longitudinal directions.

An especially desirable construction comprises a staple A tricot fabric was knit from two bars, the front bar being knit in a 1-0/0-1 stitch pattern from 20/1 cotton count staple fiber yarns made up of 80% secondary cellulose acetate and 20% nylon two inch staple fibers of 3 denier; the staple fiber yarns contained 15 Z turns of twist per inch. The rear bar was knit in a 34/10 stitch pattern from 15 0/ 2Z/ 40 cellulose triacetate filament yarns. (The acetyl value of the secondary cellulose acetate was 55% and that of the cellulose triacetate was 61% calculated as combined acetic acid by weight.) The fabric was knit 14 gauge with 30 courses per inch to a width of. 168 inches, the front yarns making up 48% of the total fabric weight. The fabric was slit into 56 inch widths, each narrow strip being bunched laterally and immersed for about 40 seconds in water at 205 F., the strips being reduced in width to 49 inches. The strips were winch bleached for 45 minutes at 180 F. with a solution having a pH of about 5.5 and containing, on the weight of the fabric, 5% of peracetic acid, 1% of caustic'soda and 4.0% of sodium hexametaphosphate. The fabric strips were finished by rinsing with 1.0% of a quaternary ammonium cationic softener. The strips were then passed on pins through a heating unit provided with a first section at about 300 F. to effect drying and a second section at about 385 F. to effect heat treatment; the residence time of the fabrics was about 30 seconds in the first section and about 20 seconds in the second section.

The fabrics were then subjected to mechanical compaction in longitudinal direction. The fabric strips were then roller printed with a resin bonded pigment, the printing being carried out under conditions of minimum tension. The fabrics were then dried in open width without tension and cured at about 275 F. for about 7 minutes. The finished fabric exhibited marked dimensional stability even after five washings, as evidenced by low shrinkage in both length and width.

It will be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made without departing from the spirit of my invention.

Having thus described my invention, what I desire to secure and claim by Letters Patent is:

l. The method of imparting marked dimensional stability to a multi-bar warp knit fabric comprising at least about 50% by weight of crystallizable heat settable thermoplastic filamentary material which comprises wetting out said fabric with hot water at a temperature of at least about 190 F. while said fabric is laterally unrestrained thereby permitting said fabric to contract laterally, then drying said fabric at a temperature of about 225 to 250 F., heat treating said dried fabric at a temperature of about 375 to 400 F. to effect setting of the thermoplastic filamentary material, and subsequently subjecting said fabric to mechanical compaction in longitudinal direction to reduce its length to about 90 to 99% of its length before compaction, said crystallizable heat settable thermoplas References Cited in the tile of this patent UNITED STATES PATENTS 1,861,422 Cluett May 31, 1932 2,319,809 Francis May 25, 1943 2,591,861 Pannaci Apr. 8, 1952 2,613,521 Walmsley Oct. 14, 1952 2,669,502 Walmsley Feb. 16, 1954 3,001,262 Parker et al. Sept. 26, 1961 3,041,861 Kasey July 3, 1962 FOREIGN PATENTS 513,258 Canada May 31, 1955 OTHER REFERENCES Standard Handbook of Textiles, by A. J. Hall, published by the National Trade Press Ltd., London, 1959, page 301. 

1. THE METHOD OF IMPARTING MARKED DIMENSIONAL STABILITY TO A MULTI-BAR WARP KNIT FABRIC COMPRISING AT LEAST ABOUT 50% BY WEIGHT OF CRYSTALLIZABLE HEAT SETTABLE THERMOPLASTIC FILAMENTARY MATERIAL WHICH COMPRISES WETTING OUT SAID FABRIC WITH HOT WATER AT A TEMPERATURE OF AT LEAST ABOUT 190*F. WHILE SAID FABRIC IS LATERALLY UNRESTRAINED THEREBY PERMITTING SAID FABRIC TO CONTRACT LATERALLY, THEN DRYING SAID FABRIC AT A TEMPERATURE OF ABOUT 225 TO 250* F., HEAT TREATING SAID DRIED FABRIC AT A TEMPERATURE OF ABOUT 375 TO 400*F. TO EFFECT SETTING OF THE THERMOPLASTIC FILAMENTARY MATERIAL, AND SUBSEQUENTLY SUBJECTING SAID FABRIC TO MECHANICAL COMPACTION IN LONGITUDINAL DIRECTION TO REDUCE ITS LENGTH TO ABOUT 90 TO 99% OF ITS LENGTH BEFORE COMPACTION, SAID CRYSTALLIZABLE HEAT SETTABLE THERMOPLASTIC FILAMENTARY MATERIAL COMPRISING AT LEAST ONE MEMBER OF THE CLASSS CONSISTING OF CELLULOSE TRIACETATE, NYLON, POLYESTERS, VINYLIDENE CYANIDE POLYMERS AND COPOLYMERS, AND VINYLIDENE CHLORIDE POLYMERS AND COPOLYMERS. 